sorry for any confusion, like I said, storage can get complex with many parameters. To try and simplify:
I have 3 BCF in the ground, I don't want to take it out in the spot market with cash trading -.50 to Feb NYMEX as I could take it out in Feb for .50 more. But why take it out in Feb when I could take it out in March for .18 more. Repeat this until you get to the best price forward in the next withdrawal season (8.903 Feb of 2008). Due to this, I would elect to set my hedges (sales) to next Feb via NYMEX. Now, for me to take it out any earlier, the spot and/or futures market will have to trade higher in the prompts for me to sell it now. Lets say when cold comes mid-month, (forecasted now BTW), and spot trades .30 over current Feb futures, I can now withdrawal gas and buy Feb futures to reinject my gas at a lower price and cover my associated costs of tport and fuel.
Now forget spot/futures. Lets look at forward strip, I will make up prices for example.
G7 6.00
H7 6.20
J7 6.30
K7 6.40
etc.
etc.
to winter
X7 7.50
Z7 8.00
F8 8.50
G8 8.60
H8 8.40
If I had gas in the ground, I could not withdrawal and reinject at any point in this strip economically. When it gets cold, you have to price up spot and/or futures to get my gas out.
Now lets change this forward strip reflecting a return of cold induced demand:
G7 7.50
H7 7.60
J7 7.10
K7 6.90
M7 6.98
N7 7.10
Q7 7.20
U7 7.30
V7 7.50
X7 7.90
Z7 8.50
F8 8.80
G8 8.90
H8 8.60
With this curve, I would now withdrawal my gas in March and buy futures as a hedge for reinjecting it in May all while leaving my forward sales in Feb of 2008 intact.
Does this help?